Monday 21 November 2005 07.25 EST
First published on Monday 21 November 2005 07.25 EST

The following correction was printed in the Guardian's Corrections and clarifications column, Tuesday November 22 2005

The above headline on this article may have given the impression that the Eden Project itself was involved in the new project. To clarify, it is the team of architects behind the Eden Project in Cornwall who are planning to turn a Lancashire rubbish dump into a rainforest. The Eden Project itself is not involved in the proposal.

The team of architects behind the Eden Project in Cornwall is planning to turn a Lancashire rubbish dump into a tropical rainforest which would heat itself with decomposing garden and kitchen waste.

The £150m proposal, dubbed "Kew of the North", could become a tourist site to rival Eden and regenerate a large area of derelict land near the M6. It includes one of England's highest waterfalls, walkways through the treetops and possibly Europe's biggest compost heap, capable of using most of the green waste of a city the size of Manchester.

One of the attractions of the proposal would be its negligible running costs, said Michael Pawlyn, a director of architects Grimshaw, who worked on the Eden Project for seven years. "The scale would be pretty vast, 25% bigger than Eden. A lot of local authorities are in a flap over what to do with their waste. The idea is to turn the problem into an opportunity."

Grimshaw, working with waste engineers, is developing the idea of the Georgian pineapple growing sheds at the Lost Gardens of Heligan in Cornwall. These are heated by bark and horse manure and grow up to 300 exotic vegetables and fruit.

The architects would build 50 metre high walls out of rubble, which would contain "bio-digester" composting tubes. Into these would be fed household and municipal waste such as leaves, grass cuttings, tree prunings, soil, waste food and even some textiles and paper.

Heat exchange tubes would then transfer low-grade heat emissions into the glass-roofed space to create the warm, saturated environment needed for rainforest life. A byproduct of the process would be thousands of tonnes of high-quality compost, which could be sold and would reduce the amount of peat dug up.

Unlike Eden, which uses fossil fuels to heat its domes in winter, Kew of the North is expected to get its fuel for free and would run at a profit even without visitors. Civil engineers working with Grimshaw estimate that it could earn about £12m a year by generating heat and electricity on site and from taking the green waste.

The demand for large-scale composting in Britain is booming because of ambitious European targets which insist that local authorities recycle more and more biodegradable waste. Local authorities pay £20 to £30 a tonne to get rid of it and can be fined £150 a tonne if they do not meet their targets.

The site of the proposal has been withheld while the regeneration group which commissioned the designs decides whether it is feasible. However, Grimshaw said the design was applicable to landfill sites around Britain. Its name could also be changed to reflect where it is built.

One of the benefits, said Mr Pawley, would be to stimulate thinking about what we throw away. "It's hard to visit a landfill site without being struck by the craziness of taking very valuable minerals and resources out of the ground using a lot of energy, turning them into short life products and then just dumping them back into the ground. It's an absolutely monumental waste of energy and resources. As someone from the fashion industry might say, it's just so last century."

"This scheme recovers heat which is usually wasted," said Jane Gilbert, chief executive of the the Composting Association. "If it's growing a rainforest people would be able to see the benefits of recycling. It sounds like win-win-win."